Many wireless communication systems use communication stations (base stations, eNodeBs, eNBs) to provide geographical service areas where wireless communication user equipment devices (UE devices) communicate with the communication station providing the particular geographical service area in which the UE devices are located. The communication stations are connected within a network allowing communication links to be made between the wireless communication devices and other devices. The communication system may include communication stations that provide overlapping service areas of different sizes to serve various needs of mobile UE devices. For example, macrocell communications stations may provide macrocell service areas that are larger and may cover one or more small cell service areas provided by small cell communication stations.
In some circumstances, the communication links are between wireless communication UE devices that are close to each other. In these situations, it may be preferred to have a direct communication link between the two wireless UE devices rather than communicating through a base station. Such direct communication between devices is often referred to as device-to-device (D2D) communication or peer-to-peer (P2P) communication. The communication resources (e.g., time frequency blocks) used for D2D communication are typically a subset of the communication resources used by the communication system for communication between UE devices and the communication stations.
An in-coverage UE device (InC UE device) is a UE device that is within the service area of a communication station and is capable of communication with the communication station. An out-of-coverage UE device (OoC UE device) is a UE device that is not within a service area of any communication station. D2D UE devices that are engaged in D2D communication with each other form a D2D group. A D2D group, therefore, includes two or more D2D UE devices. There are five typical coverage scenarios that occur with D2D groups. In a first coverage scenario, all the UE devices of the D2D group are located in a service area of a single communication station. For the first scenario, therefore, all of the D2D UE devices of the D2D group are InC UE devices in a single service area. In a second coverage scenario, none of the UE devices of the D2D group are located inside any service area of any communication station. For the second scenario, therefore, all of the D2D UE devices of the D2D group are OutC UE devices. In a third coverage scenario, at least one of the UE devices of the D2D group is located in a service area of a single communication station and at least one D2D UE device of the group is outside all service areas. For the third scenario, therefore, at least one of the D2D UE devices of the D2D group is InC UE device in a single service area and at least one UE device is an OutC UE device. The third coverage scenario is sometimes referred to as a partial coverage scenario. In a fourth coverage scenario, at least one of the UE devices of the D2D group is located within a first service area of a first communication station and at least one D2D UE device of the group located within a second service area of a second communication station. For the fourth scenario, therefore, at least two of the D2D UE devices of the D2D group are InC UE devices in different service areas. In a fifth coverage scenario, at least one of the UE devices of the D2D group is located within a first service area of a first communication station, at least one D2D UE device of the group located within a second service area of a second communication station, and at least one UE device of the D2D group is an OoC UE device. For the fifth scenario, therefore, at least two of the D2D UE devices of the D2D group are InC UE devices in different service areas and at least one D2D UE device of the group is an OoC UE device. Other coverage scenarios are possible. Since the UE devices of a group are mobile, there are situations where the coverage scenario of a D2D group changes. For example, where only one UE device of a D2D group is in coverage and moves out of coverage, the coverage scenario changes from a partial coverage scenario to an out of coverage scenario.